Establishment of a quantitative PCR assay for the detection of lymphocystis disease virus (LCDV) in olive flounder (Paralichthys olivaceus)

다국어 초록 (Multilingual Abstract)

Lymphocystis disease (LCD), characterized by gray nodules formed by hypertrophied cells on the skin and fins, reduces the commercial value of affected fish in both aquaculture and ornamental fish industries. Due to the long-term persistence of lymphocystis disease virus (LCDV) in infected fish and its potential for horizontal transmission, early detection before the onset of visible lesions is important to prevent its spread. In this study, a rapid and reliable quantitative PCR (qPCR) assay targeting the major capsid protein (MCP) gene of LCDV genotype II isolated from olive flounder (Paralichthys olivaceus) was developed. The assay exhibited acceptable amplification efficiency, linearity, and specificity. No non-specific amplification was detected in tissues from uninfected fish. The qPCR assay sensitively detected LCDV DNA not only in external tissues, such as fin, gill, and muscle, but also in internal organs, including kidney and liver, during experimental infection. These results demonstrate that the developed qPCR assay provides a sensitive and quantitative method for detecting LCDV genotype II in both symptomatic and asymptomatic olive flounder and represents a useful tool for disease surveillance and future investigations on viral infection dynamics in aquaculture.